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Sulfidated zero valent iron (ZVI) is a popular material for the reductive degradation of halogenated organic pollutants. Simple and economic synthesis of this material is highly demanded. In this study, sulfidated micro/nanostructured ZVI (MNZVI) particles were prepared by simply heating MNZVI particles and sulfur elements (S 0 ) in pure water (50℃). The iron oxides on the surface of MNZVI particles were conducive to sulfidation reaction, indicating the formation of iron-sulphide minerals (FeS x ) on the surface of MNZVI particles might not be from the direct reaction of Fe 0 with S 0 (Fe 0 and S 0 acted as reductant and oxidant, respectively). As an important reductant, hydrogen atom (H•) can be generated from the reduction of H + by MNZVI particles and participate in the formation of FeS x . Quenching experiment and cyclic voltammetry analysis proved the existence of H• on the surface of MNZVI particles. DFT calculation found that the potential barrier of H•/S 0 and Fe 0 /S 0 were 1.91 and 7.24 eV, respectively, indicating that S 0 would preferentially react with H• instead of Fe 0 . The formed H• can quickly react with S 0 to generate hydrogen sulfide (H 2 S), which can further react with iron oxides such as α-Fe 2 O 3 on the surface of MNZVI particles to form FeS x . In addition, the H 2 partial pressure in water significantly affected the amount of H• generated, thereby affecting the sulfidation efficiency. For TCE degradation, as the sulfur loading of sulfidated MNZVI particles increased, the contribution of H• significantly decreased while the contribution of direct electron transfer increased. This study provided new insights into the synthesis mechanism of sulfidated ZVI in water., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

The effects of hydrogen absorption on the local lattice structure in palladium (Pd) were investigated by means of positron annihilation lifetime spectroscopy (PALS) and time-differential perturbed angular correlation (TDPAC) spectroscopy. The PALS measurements demonstrated that dislocations and vacancies formed in the preparation process of a pristine Pd plate can be clearly removed by vacuum annealing at 1073 K and the subsequent absorption of a large quantity of hydrogen, resulting in the production of the β-phase hydride PdH0.62, induces the formation of the open-volume defects again. It was also found that the absorbed hydrogen atoms remain in the Pd sample at 323 K but they are completely evacuated during 5 h heating at 383 K. In addition to the overall thermal behavior, an atomic scale observation of the hydrogen dynamics was carried out by means of TDPAC spectroscopy, indicating the nuclear quadrupole relaxation of the present (111m,111Pd → 111Ag→)111Cd probe, which evidently suggests that the hydrogen atoms show fast dynamic motion around the probe. From the temperature-dependent nuclear quadrupole relaxation rate, we obtained an activation energy of 41(4) meV for the motion. [ABSTRACT FROM AUTHOR]

The photocatalytic hydrogen (H 2) production has gained much interest in the past decades. Alcohol was typically used as a sacrificial reagent for the H 2 evolution reaction. In the present work, the effect of primary alcohol on the photocatalytic H 2 production over the CuO/NiO/NiFe 2 O 4 composite was investigated. The composite was derived by calcining a CuO/NiFe-layered double hydroxide mixture at 973 K for 4 h. Through the synergistic effect of three components, the composite exhibited higher photocatalytic activity than the pristine CuO and NiO/NiFe 2 O 4 under UV–visible light. The H 2 production over CuO/NiO/NiFe 2 O 4 increased from 50.3 μmol to 265.3 μmol upon the changing of sacrificial reagent from methanol to butanol as supported by the increase of the cathodic photocurrent in butanol aqueous solution. The insight mechanism was detailed by theoretical calculation. The co-adsorption of butanol on the catalyst surface resulted in a decrease in hydrogen atom adsorption-desorption free energy, which consisted of the higher H 2 evolution activity compared to that of methanol system. [Display omitted] • CuO/NiO/NiFe 2 O 4 composite was prepared by heating CuO/NiFe layered double hydroxide. • The heterostructure formation improved charge separation and H 2 production. • With methanol and butanol, the AQY at 400 nm rose from 0.42% to 1.2%, respectively. • A higher activity in butanol system was supported by a decrease in H ad/desorption free energy. [ABSTRACT FROM AUTHOR]

Recently, direct non-oxidative conversion of methane (NOCM) into hydrogen and light hydrocarbons has garnered considerable attention. In our work, we employed a dielectric barrier discharge (DBD) plasma over a GaN/SBA15 catalyst for NOCM. Adding catalyst to plasma remarkably promotes the conversion of CH4, resulting in a significant improvement, for instance, from 27.8 to 39.2%. A systematic investigation of plasma performance at different discharge powers with and without catalyst was conducted. In the case of plasma + 15wt% GaN/SBA15, CH4 conversion reaches an impressive 79.4%. However, it exhibits the lowest selectivity of 14.4% for C2+, while achieving the highest selectivity for hydrogen at 48.9%. Several characterization methods, including XRD, SEM, BET, XPS, and TPO-MS, were used to study the mechanism of the reaction. Plasma electrons and ions can effectively interact with activated CH3 radicals, promoting their adsorption onto Ga sites on the catalyst surface. Simultaneously, hydrogen atoms adsorb onto neighboring N atoms, rapidly delocalizing to produce H2, and the delocalization of hydrogen atoms in C species leads to the formation of species like CxHy. This study highlights the potential of plasma catalysis in significantly improving CH4 conversion at lower temperatures and atmospheric pressure. [ABSTRACT FROM AUTHOR]

Trapping of hydrogen atoms by defects in the crystal lattice of various iron phases is an important factor in the theoretical description of the mechanisms of hydrogen embrittlement in steels. This paper provides a brief overview of our studies of the interaction of hydrogen with point defects and phase boundaries in BCC-iron alloys using ab initio calculations. The capture of hydrogen atoms by alloying impurities, as well as by vacancies (Va) and vacancy complexes VaHn, grain boundaries (GBs), and the ferrite/cementite interphase boundary, is considered. A hierarchical map of trapping energies associated with common crystal-lattice defects is presented, and the most attractive sites for H traps are identified. The influence of V and Ti alloying impurities on the interaction of H with BCC iron is considered. [ABSTRACT FROM AUTHOR]

The exchangeability of hydrogen atoms within organic molecules in vivo with ambient water hydrogen is uncertain. We assessed this by administrating the tracer deuterium to the fish. Flatfish were retained in deuterium-elevated seawater for 48 h, and the deuterium-to-hydrogen (D/H) ratios in the flesh samples were measured. Rapid in vivo equilibration between exchangeable organically bound hydrogen (Ex-OBH) and tissue-free water (TFW) hydrogen was indicated by the linear relationship between the D/H ratios of total organically bound hydrogen (t-OBH) and TFW. The estimated ratio of Ex-OBH to t-OBH (fe) in vivo was 7.2 ± 0.0%, while there was no in vivo production rate of non-exchangeable organically bound deuterium (Nx-OBD). In contrast to this estimation of no production of Nx-OBD in vivo , the D/H values of Nx-OBH measured by equilibration in vitro increased, consequently reducing the value of fe in vitro to some extent compared to that of fe in vivo. This indicated that a certain portion of Ex-OBH in vivo was not exchangeable during the equilibration in vitro. [ABSTRACT FROM AUTHOR]

The search for water on Mars has long been a theme of intense exploration, as it represents a means of addressing Mars' current climate as well as its evolution in the recent and more distant past. Since the 1970s, several missions have carried instruments to track water in the atmosphere, leading to the conceptualization of a water cycle on Mars characterized by intense seasonal variability in water vapor abundance across the planet. After Mariner 9, Viking, Phobos 2 and Mars Global Surveyor, Mars Express has become the fifth orbiter capable of detecting water vapour, with unique features: measurements by several instruments, each probing a distinct wavelength region from near-infrared to thermal infrared, altitude-dependent profiling of water thanks to solar occultation, and observation in the exosphere of its by-product, hydrogen atoms, which can escape into space, depriving Mars of its primordial water reservoir. Thanks to Mars Express, a new vision of Mars' water cycle and escape processes has emerged. The achievements of Mars Express, as well as the legacy of other missions, which established the foundations of our understanding of Mars' water cycle are presented in this article. [ABSTRACT FROM AUTHOR]

[Display omitted] • A microorganism template strategy is used to construct cobalt-phosphide-graphene. • This designed catalyst has comparable HER performance in acidic electrolyte. • The charge redistribution between Co 2 P and pyrrole-N interprets boosted activity. Developing highly efficient and sustainable hydrogen evolution reaction (HER) electrocatalysts is important for the practical application of emerging energy technologies. The spherical structure and phosphorus-rich properties of Chlorella can facilitate the construction of comparable transition metal phosphide electrocatalysts. Here, a microorganism template strategy is proposed to construct a cobalt-phosphide-graphene hybrid. Chlorella can absorb metal ions, and the generated rough spherical nanoparticles are uniformly distributed around the reduced graphene oxide nanosheets. This designed catalyst has comparable HER performance in acidic electrolytes and needs an overpotential of only 153 mV at a current density of 10 mA cm−2. The experimental and density functional theory results imply that the charge redistribution between Co 2 P and pyrrole-N is the key factor in enhancing the HER activity. The induced electron aggregation at the N and P sites can serve as a key active site for absorbing the adsorbed hydrogen atom intermediate to accelerate the HER process, contributing to the active sites of Co 2 P- and pyrrole- N -doped carbon with 0 eV hydrogen adsorption free energy. This work provides a broad idea for synthesizing advanced catalysts by a biological template approach, facilitating the innovative integration of biology and emerging electrochemical energy technologies. [ABSTRACT FROM AUTHOR]

Hydrogen spillover effect has recently garnered a lot of attention in the field of electrocatalytic hydrogen evolution reactions. A new avenue for understanding the dynamic behavior of atomic migration in which hydrogen atoms moving on a catalyst surface was opened up by the setup of the word "hydrogen spillover." However, there is currently a dearth of thorough knowledge regarding the hydrogen spillover effect. Currently, the advancement of sophisticated characterization procedures offers progressively useful information to enhance our grasp of the hydrogen spillover effect. The understanding of material fabrication for hydrogen spillover effect has erupted. Considering these factors, we made an effort to review most of the articles published on the hydrogen spillover effect and carefully analyzed the aspect of material fabrication. All of our attention has been directed toward the molecular pathway that leads to improve hydrogen evolution reactions performance. In addition, we have attempted to elucidate the spillover paths through the utilization of DFT calculations. Furthermore, we provide some preliminary research suggestions and highlight the opportunities and obstacles that are still to be confronted in this study area. [ABSTRACT FROM AUTHOR]

Hydrogen spillover is an extraordinary effect in heterogeneous catalysis and hydrogen storage, which refers to the surface migration of metal particle-activated hydrogen atoms over the solid supports. Historical studies on this phenomenon have mostly been limited to reducible metal oxides where the long-distance proton-electron coupled migration mechanism has been established, yet the key question remains on how to surmount short-distance and defect-dependent hydrogen migration on nonreducible supports. By demerging hydrogen migration and hydrogenation reaction, here we demonstrate that the hydrogen spillover in nonreducible metal-organic frameworks (MOFs) can be finely modulated by the ligand functional groups or embedded water molecules, enabling significant long-distance (exceed 50 nm) movement of activated hydrogen. Furthermore, using sandwich nanostructured MOFs@Pt@MOFs as catalysts, we achieve highly selective hydrogenation of N-heteroarenes via controllable hydrogen spillover from Pt to MOFs-shell. We anticipate that this work will enhance the understanding of hydrogen spillover and shed light on de novo design of MOFs supported catalysts for many important reactions involving hydrogen. Historical studies on hydrogen spillover have primarily focused on reducible metal oxides, establishing the long-distance proton-electron migration mechanism. This study reveals that in nonreducible metal-organic frameworks, hydrogen spillover can be precisely controlled by ligand functional groups or embedded water molecules, allowing for significant long-distance hydrogen migration. [ABSTRACT FROM AUTHOR]

In this comprehensive study, we systematically investigated the mechanism of solubility and permeability of hydrogen on the surface and within the bulk structure of aluminum using density functional theory calculations. Our analysis involved determining the stable positions, diffusion energy barriers, and electronic properties of hydrogen atoms adsorbed on the aluminum (100) surface, as well as evaluating the solution energy and diffusion energy barrier of hydrogen within bulk aluminum. Our findings highlight that the OIS→TIS pathway exhibits the most probable diffusion of hydrogen atoms, characterized by the lowest barrier energy (E b = 0.138 eV). We also conducted calculations for various adsorption structures ranging from low to high coverage and determined the diffusion coefficient across a temperature range of 100–1000 K, comparing our results to experimental data. To accurately describe the interactions between surface and bulk atoms along with the adsorbate, we explored different placements of hydrogen atoms on the aluminum (100) surface. Our investigation revealed that increasing the depth of the hydrogen adsorption site from the surface for both TIS and OIS results in a decrease in the adsorption energy value. Moreover, we observed a more significant decrease in the diffusion coefficient at lower temperatures in the BS→HS transition, indicating a reduced tendency for hydrogen atoms to approach the aluminum (100) surface. The layer-dependent diffusion behavior demonstrated that as hydrogen atoms penetrate deeper into the surface, they encounter lower barrier energies and shorter diffusion lengths. Furthermore, the diffusion coefficient for hydrogen increases as it moves into the inner layers across all temperature ranges. • The mechanism of solubility and permeability of H atom on the surface and within the bulk structure of Al using DFT. • The OIS→TIS pathway shows the most probable diffusion of H atoms, characterized by the lowest barrier energy (E b = 0.138 eV). • Different placements of hydrogen atoms on the aluminum (100) surface were explored. • Increasing H adsorption depth from surface in TIS/OIS reduces adsorption energy. • As Hydrogen atoms penetrate deeper into the surface, they encounter lower barrier energies and shorter diffusion lengths. [ABSTRACT FROM AUTHOR]

The Schrödinger equation for the hydrogen atom enclosed by an impenetrable spherical cavity is solved through a Finite‐Differences approach to gain an insight on the actual nature and structure of the ansatz wavefunction cutoff factor widely used in an ad hoc manner in corresponding variational calculations to comply with the Dirichlet boundary conditions. The results of this work provide a theoretical foundation for the choice of the appropriate analytical cutoff functions that fulfill the boundary conditions. We find three different regions for the behavior of the cutoff functions. Small cavity radius where the cutoff function has a parabolic behavior, an intermediate region where the cutoff function is quasi‐linear, and a large cavity region where the cutoff function is a step‐like function. We deduce the traditional linear and quadratic cutoff functions used in the literature as well as its validity region for the confining radius. Finally, we provide a mathematical deduction of the exact cutoff function in terms of the nodal structure of the free hydrogenic wavefunctions and a relation to the Laguerre polynomials for some cavity radii where the free atomic energy level coincides with a confined energy level. We find that the cutoff function transit over several unconfined solutions in terms of its nodal structure as the system is compressed. [ABSTRACT FROM AUTHOR]

The alloys of the Ti-Zr-Mn system based on the C14-type Laves phase are considered as ones of the most promising materials for safe storage and transportation of hydrogen. These alloys have appropriate parameters for activating the processes of absorption and release of hydrogen, a low cost, and a fairly high cyclic stability. In this work, the microstructure and phase composition of the starting alloys and the crystal structure of the hydrides synthesized from them are studied. Possible ways to reduce the cost of the final products are shown. The fact that changing the method of the alloy fabrication does not significantly affect its hydrogen absorption properties is shown. On the example of the considered alloys, it is shown that, as expected, alloying with an element with a larger atomic radius that forms a stable chemical compound with hydrogen results in an increase in the hydrogen capacity. This is explained by both the increased radius of the tetrahedral interstitial sites, where hydrogen atoms are located after dissolution, and the higher total amount of the element interacting with hydrogen. [ABSTRACT FROM AUTHOR]

ffect of the hydrogen heat treatment compared with vacuum annealing in the temperature range of 500–700C on the formation of the ordered L10 -FePd phase and variations in Raman spectra of the equiatomic FePd films are studied. The hydrogen atoms introduced into the nanoscale FePd films change the electronic structure and magnetic properties and states of the film. Ordering processes are accelerated under hydrogen treatments compared with vacuum annealing. By changing of parameters of the hydrogen annealing of the FePd film, it is possible to control the phase composition, ferromagnet ←→ paramagnet-variation in the magnetic states. The Raman spectroscopy allows investigate the dynamics of structural changes in the FePd films during the ordering and the ordered L10 -FePd-phase formation. [ABSTRACT FROM AUTHOR]

Based on first principles density functional theory (DFT) methods, this study employed the Cambridge Serial Total Energy Package (CASTEP) module within Materials Studio (MS) software under the generalized gradient approximation to investigate the adsorption, diffusion behavior, and electronic properties of hydrogen atoms on α-Fe(110) and α-Fe(110)-Me (Mn, Cr, Ni, Mo) surfaces, including calculations of their adsorption energies and density of states (DOS). The results demonstrated that doping with alloy atoms Me increased the physical adsorption energy of H2 molecules on the surface. Specifically, Mo doping elevated the adsorption energy from −1.00825 eV to −0.70226 eV, with the largest relative change being 30.35%. After doping with Me, the chemical adsorption energy of two hydrogen atoms does not change significantly, among which doping with Cr results in a decrease in the chemical adsorption energy. Building on this, further analysis of the chemical adsorption of single atoms on the surface was conducted. By comparing the adsorption energy and the bond length between a hydrogen atom and iron/dopant metal atom, it was found that Mo doping has the greatest impact, increasing the bond length by 58.58%. Analysis of the DOS functions under different doping conditions validated the interaction between different alloy elements and H atoms. Simultaneously, simulations were carried out on the energy barrier crossed by H atoms diffusing into the metal interior. The results indicate that Ni doping facilitates the diffusion of H atoms, while Cr, Mn, and Mo hinder their diffusion, with Mo having the most significant effect, where its barrier is 21.88 times that of the undoped surface. This conclusion offers deep insights into the impact of different doping elements on hydrogen adsorption and diffusion, aiding in the design of materials resistant to hydrogen embrittlement. [ABSTRACT FROM AUTHOR]

The electrical properties of Pd/InP Schottky diodes and Pd-layers deposited on glass substrate by thermal evaporation in vacuum, and placed in hydrogen medium containing 10–100 vol % of hydrogen, were studied. The current generation in Pd/InP Schottky diodes, as well as the decrease in resistance of Pd layers were observed in hydrogen medium. It is proposed that the current generation in the structures under study is due to free electrons as result of hydrogen atoms ionization. The current induced by these electrons exists in electric circuit until hydrogen is present in the environment. It is shown that the hydrogen current generators can be created based on the Pd/InP diode structure. [ABSTRACT FROM AUTHOR]

Using the resonant fluorescence (RF) of chlorine atoms and iodine atoms, the rate constant of the reaction of a chlorine atom with hydrogen iodide at a temperature of 298 K is measured. The values of the reaction constants measured by both methods turns out to be quite similar. The role of this reaction in the chemistry of the troposphere above the surface of the oceans is discussed. [ABSTRACT FROM AUTHOR]

Planar hypercoordination has sparkled interest among the researchers from last few decades. Most of the elements in the Periodic Table have shown this remarkable structural feature. However, the smallest element, hydrogen, is missing in the list. No evidence is there in the literature. Herein, we introduce the first planar pentacoordinate hydrogen atom (ppH) in the global minimum geometry of Li5H6− cluster. Bonding analysis indicates that the central hydrogen atom is stabilized by multicentre bonding with five surrounding Li atoms. Natural charge analysis reveals that the central hydrogen is acting like a hydride which is strongly attracted by the positively charged surrounding lithium centres. The ppH structure is stabilized by strong electrostatic attraction as well as extensive multicentre bonding. Aromaticity has no role to play here. The cluster is dynamically stable and is expected to be detected in gas phase. [ABSTRACT FROM AUTHOR]

This study examines the evolution of the Klein-Nishina (KN) cross section for hydrogen and platinum atoms in relativistic and non-relativistic scenarios. Using online MATLAB tools, the constructed model of KN cross section for both situations is calculated. The observation demonstrates that as electron energy increases, electronic and atomic KN cross section lowers, which lessens the relationship between the incoming electron and the target atom. The importance of atomic size is demonstrated by a comparison of the KN cross sections of hydrogen and platinum, with platinum possessing a higher cross section because of its greater size and more scattering centers. Higher atomic numbers result in greater interaction between sites and bigger cross sections, and they also play a role in this relationship. The variations in cross sections are also influenced by electron binding effects, especially in the instance of hydrogen. It is demonstrated that relativistic effects have a major impact on the KN cross section, including an exponential decline seen as the energy of electrons increases. In the relativistic domain, the electron's increased mass and decreased wavelength increase scattering probability and produce a greater cross section than in the non-relativistic case. This research sheds light on the variables affecting KN cross sections and their influence on radiation therapy, medical imaging, and materials science. [ABSTRACT FROM AUTHOR]

This study investigates hydrogen diffusion in tungsten at high temperatures using molecular dynamics simulations. It explores the effect of different hydrogen concentrations on diffusion mechanisms, the interaction of hydrogen atoms with vacancy defects, and their impact on the mechanical properties of tungsten. The activation energy for hydrogen diffusion in perfect bulk tungsten with 0.1 % hydrogen concentration is calculated as 0.235 eV, with a diffusion pre-exponential factor of 5.336 × 10-8 m2/s at temperatures ranging from 1000 to 3000 K. The investigation reveals two factors contributing to the increase in activation energy with temperature: migration paths involving TIS-TIS and TIS-OIS-TIS pathways, and an increase in migration energy. Three diffusion regimes are identified, with trapping effects dominating at temperatures below 1500 K, TIS-TIS pathway dominating at intermediate temperatures, and TIS-OIS-TIS pathway becoming more prominent at higher temperatures. Increasing hydrogen concentration up to 2 % (H/W concentrations in fusion environments) has minimal effect on diffusion in perfect tungsten. However, in a W-H-V system with a 1 % vacancy defect, increasing hydrogen concentration increases the effective diffusion coefficient and activation energy. The presence of hydrogen atoms and vacancy defects reduces the tensile strength and elastic modulus of tungsten, with hydrogen atoms having a greater impact on mechanical properties compared to vacancies. The degree of reduction in mechanical properties is proportional to the concentration of hydrogen atoms and vacancy defects. • The hydrogen diffusion in tungsten at high temperatures was studied using molecular dynamics. • The study explores the effect of different hydrogen concentrations on diffusion mechanisms. • The impact of hydrogen interaction with vacancy on the mechanical properties of tungsten was studied. • The investigation reveals two factors contributing to the increase in activation energy with temperature. • The presence of hydrogen atoms and vacancy defects reduces the tensile strength and elastic modulus of tungsten. [ABSTRACT FROM AUTHOR]

Hydrogen is a crucial source of green energy and is extensively studied for its potential usage in fuel cells. The advent of 2D crystals (2DCs) has taken hydrogen research to new heights, enabling it to tunnel through layers of 2DCs or be transported within voids between the layers, as demonstrated in recent experiments by Geim's group. In this study, it investigates how the composition and stacking of transition‐metal dichalcogenide (TMDC) layers influence the transport and self‐diffusion coefficients (D) of hydrogen atoms using well‐tempered metadynamics (WTMetaD) simulations. The findings show that modifying either the transition metal or the chalcogen atoms significantly affects the free energy barriers (ΔF) and, consequently, the self‐diffusion of hydrogen atoms between the 2DC layers. In the Hhh$H^h_h$ polytype (2H stacking), MoSe2 exhibits the lowest ΔF, while WS2 has the highest, resulting in the largest D for the former system. Additionally, hydrogen atoms inside the RhM$R_h^M$ (or 3R) polytype encounter more than twice lower energy barriers and, thus, much higher diffusivity compared to those within the most stable Hhh$H^h_h$ stacking. These findings are particularly significant when investigating twisted layers or homo‐ or heterostructures, as different stacking areas may dominate over others, potentially leading to directional transport and interesting materials for ion or atom sieving. [ABSTRACT FROM AUTHOR]

Based on density functional theory, a first-principles study of the adsorption behavior of hydrogen atoms on the PuO2(111) surface is carried out in this work. Models for three different surface morphologies of PuO2(111) are established. It is found that the surface with the outermost oxygen atom (sub outer Pu atom) morphology has the best stability. Based on this model, the adsorption energy, bader charge, and electronic density of the states of a hydrogen atom at different adsorption sites are calculated. Finally, we analyzed the process of hydrogen dissociation into hydrogen atoms on the surface using the cNEB method. The results indicate that the top position of the outermost oxygen atom and the bridge position of the second outermost plutonium atom are relatively stable adsorption configurations, where hydrogen atoms lose electrons and release heat, forming O-H bonds with oxygen atoms. The density of states of O-p orbital electrons will undergo significant changes, reflecting the hybridization of O-p and H-s orbital electrons, forming a stable bonding effect. The dissociation of hydrogen molecules into two hydrogen atoms adsorbed on the top of oxygen atoms requires crossing an energy barrier of 1.06 eV. The decrease in total energy indicates that hydrogen tends to exist on the PuO2(111) surface in a hydrogen atom state. The research results lay the foundation for theoretically exploring the hydrogenation corrosion mechanism of the PuO2(111) surface, providing theoretical support for exploring the corrosion aging of plutonium oxide, predicting the material properties of plutonium oxide under extreme and special environments. [ABSTRACT FROM AUTHOR]

In this work, the crystal structure of Leptothrix biosamples was studied using positron annihilation lifetime spectroscopy, MIKA modeling package and X-ray diffraction method. The structural analysis results showed that free cubic and orthorhombic phase Fe and trigonal Fe2O3 and cubic Fe3O4 phases were detected in Leptothrix biosamples. It has been determined that the concentration of cubic Fe3O4 phases in biosamples is higher than other phases. The theoretical bases of the regularity of distribution of hydrogen and oxygen atoms in the form of free and vacancies in the trigonal Fe2O3 and cubic Fe3O4 phases were calculated. On the other hand, the lifetime of vacancies in Fe, Fe2O3 and Fe3O4 structures has been determined. [ABSTRACT FROM AUTHOR]

Magnesium is an effective catalyst for producing hydrogen through thermochemical water splitting. However, the slow reaction between Mg and water prevents this catalyst from being commercially useful. In this study, reactive MD simulations with accurate force fields and reactive potential energy surfaces are used to comprehend the slow-kinetics of the Mg-water reaction. At room temperature, water is split when it interacts with Mg nanoparticles and forms a Mg–H bond. Furthermore, at temperatures above 1200 K, Mg–H bonds begin to dissociate, resulting in the generation of hydrogen radicals from the Mg–H bond. The percentage of H–H bonds is almost zero until the reaction pathway reaches temperature 2000K, after which H radicals combine to form hydrogen gas. The analysis of temperature dependent data reveals that oxygen and hydrogen atoms combine with Mg elements to form massive stable linear and branched chains, resulting in slow Mg-water reaction kinetics for hydrogen production. Therefore, current studies utilizing reactive molecular dynamics can provide a means of improving the kinetics of the Mg-water reaction. • Water splitting process for H 2 production carried out by MD simulation. • Reason for slow reaction between Mg and H 2 O examined. • Slow reaction happened due to evolution of -H-Mg-H- and -O-Mg-O- structures. • H 2 production found at T>2000K during gradual heating. [ABSTRACT FROM AUTHOR]

Among the list of planar tetracoordinate atoms, the smallest element hydrogen is missing. No experimental and theoretical evidence have ever been put forwarded. Herein, we introduce the first planar tetracoordinate hydrogen atom (ptH) in the global minimum geometry of In4H+ cluster. Bonding analysis indicates that the central hydrogen atom is acting like a proton and significant charge transfer from the surrounding In4 framework results in a negative charge of the central hydrogen atom. The proposed global minimum geometry possesses σ‐aromaticity and the central hydrogen atom forms unusual multicentre bond with more than three centres. [ABSTRACT FROM AUTHOR]

The disproportionation reaction of ZrCo will occur at high temperature resulting in a substantial reduction of hydrogen absorption, and the driving force of which was widely accepted as the non-equivalent occupation of hydrogen atom within ZrCo hydride. However, the H atoms occupation within ZrCo alloys is still ambiguous to date. Herein, hydrogen atom occupation behaviors in ZrCo hydride were studied by thermal analysis and X-ray diffraction combined with first-principle calculation during absorption and desorption. The results shown that hydrogen atoms in ZrCo alloys were preferentially occupied 8f1 site instead of 4c2 site in the situation of x ≤ 1.4, while for the case of 1.4 ≤ x ≤ 2.0 hydrogen atoms began to occupy 4c2 site , and the order of occupation at this stage is roughly 4c2 , 8f1 and 4c2. As for the case of 2.0 ≤ x ≤ 2.5, the crystal structure expanded with the increase of x value and hydrogen atoms occupied 8f1 , 4c2 and 8e site at the same time. In the process of hydrogen desorption, hydrogen atom at 8e site was firstly released, then the 4c2 site and finally 8f1 site. We believe the work can provide some experimental basis for further research on the relationship between hydrogen occupation and hydrogen-induced disproportionation of ZrCo. [Display omitted] • Hydrogen desorption process of ZrCoH x (0 < x ≤ 2.5) is investigated by thermal analysis. • Hydrogen atoms in ZrCoH x alloys are preferentially occupied 8 f1 site in the situation of x ≤ 1.4 • Formation enthalpy of H atoms at 4 c2 and 8 f1 of ZrCoH x (x = 0.5 and x = 1.0) alloys is obtained through DFT calculations. • Hydrogen atoms occupation sites within ZrCo alloys during hydrogen absorption and desorption is proposed. [ABSTRACT FROM AUTHOR]

Experimental hydrogen loadings in titanium thin films were compared to the Mintz-Bloch model. 500 nm titanium thin films were deposited with an electron-beam evaporator onto sapphire substrates and were capped with a 10 nm palladium thin film. The titanium films were loaded with hydrogen in a custom Sievert apparatus where the pressure drop showed full hydriding at a hydrogen pressure of 2 bar and loading temperatures of 100 °C, 150 °C, 200 °C and 250 °C. Comparisons of X-ray diffractions of loaded and unloaded films showed the presence of titanium hydride in loaded films. The experimental loadings were compared to the Mintz-Bloch model where the Mintz-Bloch model overpredicted experimental loadings. This was due to the Mintz-Bloch assuming that hydride forms immediately upon hydrogen exposure in the metal. However, the difference between the experimental loading kinetics and Mintz-Bloch model was reduced as loading temperatures increased until the temperature reached 250 °C where some titanium hydride outgassing occurred. • Hydrogen loading of titanium thin films was successfully demonstrated at 100 °C, 150 °C, 200 °C, and 250 °C. • Pressure drops from Sievert apparatus show hydrogen absorption of stoichiometric ratio of 2 hydrogen atoms per titanium atom. • Hydrogen absorption in titanium was confirmed with X-ray diffraction of titanium hydride peak. • Loading kinetics of titanium films compared to Mintz-Bloch model and showed good correlation. [ABSTRACT FROM AUTHOR]

Interaction between hydrogen atoms and dislocations is studied in the iron-, nickel-, and titanium-based alloys using ab initio calculations and experimental studies of the electron structure, as well as mechanical spectroscopy. It is obtained that hydrogen increases the density of electron states, DOS, at the Fermi level, which is responsible for the increased concentration of free electrons decreasing thereby the elasticity moduli, and results in the decreased line tension of dislocations causing their increased mobility. By means of mechanical spectroscopy, the hydrogen diffusion enthalpy, ΔH d , and that of binding between hydrogen atoms and dislocations, ΔH b , have been measured. It is shown that these values control temperature T c for condensation of hydrogen atoms at dislocations. Consequently, in a definite range of temperatures and strain rates, dislocations move accompanied by hydrogen atmospheres, which is a reason for hydrogen embrittlement. Hydrogen embrittlement in the iron-, nickel- and titaniun-based alloys is analyzed in terms of this concept. Based on the obtained results, the use of hydrogen as a temporary alloying element increasing techological plasticity of β titanium alloys is interpreted. [Display omitted] •Joint hydrogen-dislocation slip is a precondition for embrittlement. •Temperature range of HE is controlled by H diffusion and binding to dislocations. •Hydrogen enhances plasticity in the absence of hydrogen dislocation atmospheres. [ABSTRACT FROM AUTHOR]

Hydrogen around dislocation has a great influence on the mechanical properties of Titanium (Ti) alloys. In this study, the diffusion of hydrogen around dislocations in α-Ti alloys is investigated by coupling density functional theory (DFT) calculations and the elasticity method. Initially, the attempt frequency and hopping activation energy of hydrogen atom in the α-Ti lattice are calculated using the DFT method under various simple strain fields, including volume strain, biaxial strain, and shear strains, within a strain range of −2%–2 %. It is observed that both volume strain and biaxial strain have the most pronounced effects on the hopping activation energy of hydrogen atom, while the attempt frequency remains relatively unaffected across different strain conditions. Subsequently, the hopping activation energy in the elastic strain field has been parameterized using an elasticity method based on elastic dipole and diaelastic polarizability. Using the elasticity method, an analysis is conducted on the effective activation energy of hydrogen atoms and their hopping tendencies in the Volterra elastic strain fields around the perfect edge and screw dislocations. The elastic strain field around screw dislocation enhances the diffusion of hydrogen atoms and simultaneously promotes their migration toward the dislocation core. In the vicinity of edge dislocation, the tensile elastic strain field enhances the diffusion of hydrogen atoms and facilitates their migration toward the dislocation core. Conversely, the compressive strain field retards the diffusion of hydrogen atoms and promotes their migration away from the dislocation core or towards regions with tensile strain. • The elastic strain field around screw dislocation enhances hydrogen diffusivity. • he tensile elastic strain field of edge dislocation boosts hydrogen diffusivity. • The compressive elastic strain field of edge dislocation slows hydrogen diffusivity. • The hydrogen atom shows two distinct hopping tendencies near a screw dislocation. • The hydrogen atom shows only one hopping tendency near an edge dislocation. [ABSTRACT FROM AUTHOR]

This study revealed the relationship between V 8 C 7 size and hydrogen diffusion behavior as well as hydrogen induced cracking (HIC) in pipeline steel. Hydrogen permeation and HIC susceptibility tests were implemented on five conditions with different V 8 C 7 sizes but identical volume fractions. The results proved that with increasing of V 8 C 7 size, the hydrogen effective diffusivity was first decreased and then increased. Increasing the proportion of small size (coherent and semi-coherent) V 8 C 7 increased the effective hydrogen trapping densities, decreased hydrogen diffusion coefficient, improved the distribution of diffusible hydrogen atoms and then the HIC susceptibility of steels was decreased. • Increasing the proportion of semi-coherent V 8 C 7 is beneficial for decreasing HIC susceptibility of pipeline steel. • Coherent and semi-coherent V 8 C 7 reduced the number of dendritic cracks. • The steel with the maximum proportion semi-coherent V 8 C 7 possessed the lowest HIC susceptibility. [ABSTRACT FROM AUTHOR]

Engineering precious metals' sub‐nanometer cluster on 2D earth‐abundant supports provides a promising approach for the development of high‐efficient electrocatalysts in pursuit of green hydrogen. Herein, a novel solid phase deposition approach is demonstrated for the homogenous confinement of atomically thin Pt nanoclusters on 2D delta‐MoN as a viable catalyst for pH‐universal hydrogen evolution reaction. Notably, the optimized material (MoN‐5% Pt) exhibits excellent catalytic performance as evidenced by low overpotentials required, excellent mass activity exceeding 20 A mgPt−1 at 100 mV overpotential, and outstanding stability with negligible activity degradation. The enhanced performance is attributed to (1) novel nanostructure, constituting atomically thin Pt nanoclusters confined on 2D δ‐MoN substrate, thus rendering high atomic utilization and seamless surface mass transfer, and (2) influence of strong metal‐support interaction that effectively limits structural deformation and performance degradation. Theoretical simulations reveal that the strong metal‐support interaction induces substantial charge redistribution across the heterointerface, initiating an energy‐favorable multi‐active site microkinetics in which Pt atoms with an optimal hydrogen adsorption energy making way for enhanced H2 evolution, while Mo atoms situated at the heterointerface enhance water absorption/dissociation steps, enriching the catalytic surface with adsorbed hydrogen atoms. [ABSTRACT FROM AUTHOR]

Pd-containing catalysts (1% Pd/Al2O3 and 5% Pd/Al2O3) supported on aluminum oxide were studied in the decomposition reaction of hydrazine monohydrate. According to in situ IR-spectroscopic data, hydrazine monohydrate was adsorbed in a linear form on the coordinatively unsaturated sites of the catalyst surface. As the temperature was increased, the adsorbed hydrazine monohydrate lost a water molecule with a change in the geometry of the molecular complex. The adsorption of hydrazine on a support and its diffusion onto palladium clusters is a more advantageous process than direct adsorption on active sites. This circumstance shows that the hydrazine adsorbed on the support can be an intermediate in the process of its decomposition. The test catalysts had a maximum activity at a temperature of about 100°C. At temperatures in a range of 100−120°C, the ratio between hydrogen and nitrogen concentrations in the reaction products was 2, which corresponds to 100% selectivity for hydrogen. The selectivity decreased significantly with the reaction temperature. The high selectivity for hydrogen at low temperatures was explained by the fact that N2H4 was chemisorbed through the formation of hydrogen–metal bonds. The hydrogen–metal bond strength in such a complex is higher than the nitrogen–metal bond strength; hence, the N−H bond breaking barrier is lower than the N−N bond breaking barrier, and this fact led to the breaking of an N–H bond and the preservation of an N–N bond. At elevated temperatures, some of the formed hydrogen atoms recombined, and the other reacted with the surface complexes of hydrazine to form the intermediate NH3−NH3, in which N–N bond breaking led to the appearance of ammonia molecules in the gas phase. [ABSTRACT FROM AUTHOR]

The catalytic reduction in carbon dioxide is a crucial step in many chemical industrial reactions, such as methanol synthesis, the reverse water–gas shift reaction, and formic acid synthesis. Here, we investigate the role of bulk hydrogen, where hydrogen atoms are found deep inside a metal surface as opposed to subsurface ones, upon CO2 reduction over a Ni(110) surface using density functional theory and ab initio molecular dynamics simulations. While it has previously been shown that subsurface hydrogen stabilizes CO2 and can aid in overcoming reaction barriers, the role of bulk hydrogen is less studied and thus unknown with regard to CO2 reduction. We find that the presence of bulk hydrogen can significantly alter the electronic structure of the Ni(110) surface, particularly the work function and d-band center, such that CO2 adsorbs more strongly to the surface and is more easily reduced. Our results show an enhanced CO2 dissociation in the presence of bulk hydrogen, shedding light on a hitherto underappreciated mechanistic pathway for CO2 reduction on metal surfaces. [ABSTRACT FROM AUTHOR]

We investigate hydrogen desorptions from monolayer and multilayer graphane analogs, namely, silicane (SiH) and germanane (GeH), by the first-principles calculations. It is found from the calculated pressure–temperature diagrams of the monolayer and multilayer SiH and GeH crystals that the hydrogen atoms can be removed by heating and reducing hydrogen partial pressure. We also perform thermal-desorption-spectroscopy measurements for the multilayer crystals in order to demonstrate the validity of the theoretical calculations, and it turns out that the theoretical results are worth believing. Our theoretical results for monolayer SiH/GeH crystals indicate monolayer SiH and GeH crystals possess high potential to find their application as a precursor to free-standing monolayer silicene and germanene, respectively. [ABSTRACT FROM AUTHOR]

Hydrogen spillover, involving the surface migration of dissociated hydrogen atoms from active metal sites to the relatively inert catalyst support, plays a crucial role in hydrogen‐involved catalytic processes. However, a comprehensive understanding of how H atoms are driven to spill over from active sites onto the catalyst support is still lacking. Here, we examine the atomic‐scale perspective of the H spillover process on a Pt/Cu(111) single atom alloy surface using machine‐learning accelerated molecular dynamics calculations based on density functional theory. Our results show that when an impinging H2 dissociates at an active Pt site, the Pt atom undergoes deactivation due to the dissociated hydrogen atoms that attach to it. Interestingly, collisions between H2 and sticking H atoms facilitate H spillover onto the host Cu, leading to the reactivation of the Pt atom and the realization of a continuous H spillover process. This work underscores the importance of the interaction between gas molecules and adsorbates as a driving force in elucidating chemical processes under a gaseous atmosphere, which has so far been underappreciated in thermodynamic studies. [ABSTRACT FROM AUTHOR]

Extensive studies have been performed to reveal the mechanism of alkane hydroxylation by high-valent non-heme FeIVO species in TauD-J and synthetic complexes. However, the fundamental differences in mechanism based on spin state have not yet been fully understood. To explicate the mechanism at an atomistic level, DFT potential energy surfaces were calculated along the intrinsic reaction coordinate of hydrogen abstraction. The Fe–O bond length change and hydrogen atom transfer occur with high asynchronicity, and only quintet FeIVO complexes use a transient FeIII-oxyl species for hydrogen abstraction. TauD-J uses both the σ- and π-pathways for hydrogen transfer, rendering it more reactive than synthetic complexes. The quintet σ-pathway involves the donation of α-electrons to the σ Fe - O ∗ orbital from both axial ligands and the C–H bond, which produces the FeIII-oxyl species. However, electron donation from the axial ligands may impede further electron transfer from the C–H bond, disrupting the hydrogen transfer process and reducing the tunneling effect. Conversely, the σ Fe - O ∗ orbital in the triplet π-pathway accepts both α- and β-electrons from the axial ligands, resulting in a swift elongation of the Fe–O bond length without generating the FeIII-oxyl species. This process does not affect hydrogen transfer as the π Fe - O ∗ orbital receives electrons from the C–H bond. This distinction clarifies why the tunneling effect is greater in the triplet state. Overall, this research offers insight into the detailed mechanism of hydrogen abstraction, emphasizing the role of axial ligands and spin-dependent reactivity. [ABSTRACT FROM AUTHOR]

In this study, the effect of alloying elements on the adsorption and dissociation behaviors of hydrogen molecules on the bcc-Fe (001) surface has been investigated using first-principles calculations. H2 molecules can easily dissociate on the hollow site, and the dissociated hydrogen atoms bond with the surrounding metal atoms. Doping Cr and Mo atoms on the surface would reduce the H2 molecule adsorption energy, which promotes the H2 molecule adsorption and dissociation. When only one or two Ni atoms doping on the surface, it improves the adsorption energies, which in turn can hinder the H2 molecule adsorption and dissociation. However, three or four Ni atoms doping on the surface is beneficial to the H2 molecule adsorption and dissociation. Thus, the nickel content in Ni–Cr–Mo steel should be reasonably controlled to improve the hydrogen embrittlement resistance of the steel. [ABSTRACT FROM AUTHOR]

Quantum mechanics teaches that before detection, knowledge of particle position is, at best, probabilistic, and classical trajectories are seen as a feature of the macroscopic world. These comments refer to detected particles, but we are still free to consider the motions generated by the wave equation. Within hydrogen, the Schrodinger equation allows calculation of kinetic energy at any location, and if this is identified as the energy of the wave, then radial momentum, allowing for spherical harmonics, becomes available. The distance across the real zone of radial momentum is found to match semi-integer wavelengths of the adjusted matter wave, consistent with what is expected from a standing wave condition. The approach is extended to include orbital motions, where it is established that the underlying wave, which has direction and wavelength at each location, forms a series of connected trajectories, which are shown to be ellipses orientated at various angles to the equatorial plane. This suggests that wave trajectories, rather than particle trajectories, are still a feature of the hydrogen atom. The finding allows the reason for the coincidence between energy results derived by Sommerfeld's classical trajectories and the Schrodinger wave equation to be appreciated. The result has implications when the relativistic situation is considered, as Sommerfeld's correct deduction of the relativistic energy levels of hydrogen well before Dirac derived his wave equation has long been somewhat puzzling. [ABSTRACT FROM AUTHOR]

Due to the relatively high abundance of hydrogen radicals in the interstellar medium, the H-addition reaction of unsaturated organic molecules in the solid phase and at very low temperatures is considered to play an important role in the chemical complexity of organic substances in the Universe. However, when interacting with hydrogen atoms, all unsaturated functional groups that may be present in several organic species exhibit different behaviours that can significantly alter the reaction pathways from one species to another. By coupling FTIR spectroscopy and temperature programmed desorption mass spectrometry, we have investigated the H + c-C3H2O (cyclopropenone) solid-state reaction using two different experimental methods. We show that cyclopropenone reacts with hydrogen atoms under interstellar medium conditions, leading to propynal (HCCCHO), propadienone (CH2CCO), and two thermodynamically most stable isomers of c-C3H2O. In excess of H atoms, the hydrogenation of cyclopropenone also leads to propenal (CH2CHCHO), propanal (CH3CH2CHO), c-C3H4O (cyclopropanone), in addition to two alcohols, namely cyclopropanol (c-C3H6O) and propanol (CH3CH2CH2OH). [ABSTRACT FROM AUTHOR]

Hydrogen spillover is the migration of activated hydrogen atoms from a metal particle onto the surface of catalyst support, which has made significant progress in heterogeneous catalysis. The phenomenon has been well researched on oxide supports, yet its occurrence, detection method and mechanism on non-oxide supports such as metal–organic frameworks (MOFs) remain controversial. Herein, we develop a facile strategy for efficiency enhancement of hydrogen spillover on various MOFs with the aid of water molecules. By encapsulating platinum (Pt) nanoparticles in MOF-801 for activating hydrogen and hydrogenation of C=C in the MOF ligand as activated hydrogen detector, a research platform is built with Pt@MOF-801 to measure the hydrogenation region for quantifying the efficiency and spatial extent of hydrogen spillover. A water-assisted hydrogen spillover path is found with lower migration energy barrier than the traditional spillover path via ligand. The synergy of the two paths explains a significant boost of hydrogen spillover in MOF-801 from imperceptible existence to spanning at least 100-nm-diameter region. Moreover, such strategy shows universality in different MOF and covalent organic framework materials for efficiency promotion of hydrogen spillover and improvement of catalytic activity and antitoxicity, opening up new horizons for catalyst design in porous crystalline materials. Hydrogen spillover in MOFs is a debated research topic. Here the authors design a research platform for evaluating hydrogen spillover in MOFs and investigate water molecules how to assistant active hydrogen to improve hydrogen spillover in MOFs. [ABSTRACT FROM AUTHOR]

The diffusion behavior of hydrogen in steel plays a significant role in understanding the mechanism of hydrogen embrittlement which may lead to the failure of steel. In the present work, density functional theory based first-principles calculations were performed to investigate the hydrogen diffusion in Fe 4 N at atomic level. The results showed that the hydrogen atom in the Fe 4 N structure didn't diffuse until the temperature increased up to 1350K, indicating a layer of Fe 4 N covering on the iron could be a good candidate to trap the highly diffusive hydrogen atoms and prevent the aggregation of hydrogen which is the precursor of hydrogen embrittlement. • The H atom has a high diffusion energy barrier in Fe 4 N and didn't diffuse until the temperature increases up to 1350 K. • The H atom acts as an electron acceptor in Fe 4 N, while it acts as an electron donor in α-Fe 2 O 3. • A dense layer of Fe 4 N covering on the substrate metal may prevent hydrogen embrittlement. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) have wide‐ranging applications, and their host–guest interactions play an essential role in the achievement of COF functions. To investigate these host–guest interactions, it is necessary to locate all atoms, especially hydrogen atoms. However, it is difficult to determine the hydrogen atomic positions in COFs because of the complexities in synthesizing high‐quality large single crystals. Three‐dimensional electron diffraction (3D ED) has unique advantages for the structural determination of nanocrystals and identification of light atoms. In this study, it was demonstrated for the first time that the hydrogen atoms of a COF, not only on the framework but also on the guest molecule, can be located by 3D ED using continuous precession electron diffraction tomography (cPEDT) under cryogenic conditions. The host–guest interactions were clarified with the location of the hydrogen atoms. These findings provide novel insights into the investigation of COFs. [ABSTRACT FROM AUTHOR]

The slow‐strain‐rate test (SSRT) is the most commonly used method for evaluating pipeline steel in service environments. However, to accurately assess the sensitivity of steel to hydrogen, it is necessary to investigate the effect of different strain rates, taking into account microstructure‐influenced hydrogen migration. Herein, a hot‐rolled X70 pipeline steel sheet is investigated by a SSRT at different strain rates with and without synchronous hydrogen charging. The influence of the pearlite content and different strain rates on the hydrogen‐assisted crack propagation and hydrogen diffusion in pipeline steels is discussed. Using scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy, and hydrogen microprinting, the hydrogen atoms are observed to be easily segregated at the ferrite/pearlite (F/P) interface without external stress. Under loading, a higher strain rate results in lower hydrogen permeation content in steel, penetrating into pearlite and interacting with its internal vacancies, leading to transgranular fracture initiating from pearlite. At a low strain rate, the F/P interface is more vulnerable to hydrogen degradation, leading to intergranular crack mode along the interface and increased tendency to form secondary cracks. Therefore, strain rate–induced crack initiation and propagation characteristics should be considered during the SSRT. [ABSTRACT FROM AUTHOR]

Amorphous hafnium dioxide (a-HfO2) is widely used in electronic devices, such as ultra-scaled field-effect transistors and resistive memory cells. The density of oxygen vacancy (OV) defects in a-HfO2 strongly influences the conductivity of the amorphous material. Ultimately, OV defects are responsible for the formation and rupture of conductive filament paths which are exploited in novel resistive switching devices. In this work, we studied neutral OV in a-HfO2 using a b i n i t i o methods. We investigated the formation energy of OV, the binding energy of di-OVs, the OV migration, unperturbed and in the close presence of a hydrogen atom, as well as the migration of hydrogen atom towards OV. A shallow and short-range OV migration barrier (0.6 eV) exists in a-HfO2 in contrast to the barrier (2.4 eV) in crystalline HfO2. Nearby hydrogen has a limited impact on the OV migration; however, hydrogen can diffuse easily by hopping among OVs. [ABSTRACT FROM AUTHOR]

Amorphous hafnium dioxide (a-HfO2) is widely used in electronic devices, such as ultra-scaled field-effect transistors and resistive memory cells. The density of oxygen vacancy (OV) defects in a-HfO2 strongly influences the conductivity of the amorphous material. Ultimately, OV defects are responsible for the formation and rupture of conductive filament paths which are exploited in novel resistive switching devices. In this work, we studied neutral OV in a-HfO2 using a b i n i t i o methods. We investigated the formation energy of OV, the binding energy of di-OVs, the OV migration, unperturbed and in the close presence of a hydrogen atom, as well as the migration of hydrogen atom towards OV. A shallow and short-range OV migration barrier (0.6 eV) exists in a-HfO2 in contrast to the barrier (2.4 eV) in crystalline HfO2. Nearby hydrogen has a limited impact on the OV migration; however, hydrogen can diffuse easily by hopping among OVs. [ABSTRACT FROM AUTHOR]

Thermal oxidation and hydrogen annealing were applied on a 100 μm thick Al-doped p-type 4H-SiC epitaxial wafer to modulate the minority carrier lifetime, which was investigated by microwave photoconductive decay (μ-PCD). The minority carrier lifetime decreased after each thermal oxidation. On the contrary, with the hydrogen annealing time increasing to 3 hours, the minority carrier lifetime increased from 1.1 μs (as-grown) to 3.14 μs and then saturated after the annealing time reached 4 hours. The increase of surface roughness from 0.236 nm to 0.316 nm may also be one of the reasons for limiting the further improvement of the minority carrier lifetimes. Moreover, the whole wafer mappings of minority carrier lifetimes before and after hydrogen annealing were measured and discussed. The average minority carrier lifetime was up to 1.94 μs and non-uniformity of carrier lifetime reached 38% after 4-hour hydrogen annealing. The increasing minority carrier lifetimes could be attributed to the double mechanisms of excess carbon atoms diffusion caused by selective etching of Si atoms and passivation of deep-level defects by hydrogen atoms. [ABSTRACT FROM AUTHOR]

In the current article, utilizing the theory of quantization of time and space and the internal structure of elementary particles, the radiation spectrum of the excited hydrogen atom is calculated theoretically. By doing this, the electron movement parameters in the hydrogen atom have been stated in a novel way, and via generalizing these calculations, the excited states of other atoms can be calculated. It can be shown that during the transfer of the electron from a higher level to a lower one, what is the state of the electron in terms of momentum, energy, time, and length. [ABSTRACT FROM AUTHOR]

Alumina supported Pt nanoclusters under a hydrogen environment play a crucial role in many heterogeneous catalysis applications. We conducted grand canonical genetic algorithm simulations for supported Pt8 clusters in a hydrogen gas environment to study the intracluster, cluster-support, and cluster-adsorbate interactions. Two alumina surfaces, α-Al2O3(0001) and γ-Al2O3(100), and two conditions, T = 600 °C, p H 2 = 0.1 bar and T = 25 °C, p H 2 = 1.0 bar, were considered corresponding to low and high hydrogen chemical potential μH, respectively. The low free energy ensemble of Pt8 is decorated by a medium (2–12 H), respectively, high (20–30 H), number of hydrogen atoms under equilibrium at low μH, respectively, high μH, and undergoes different morphological transformations on the two surfaces. On α-Al2O3(0001), Pt8 is mostly 3D but very fluxional in structure at low μH and converts to open one-layer 2D structures with minimal fluxionality at high μH, whereas on γ-Al2O3(100), the exact opposite occurs: Pt8 clusters present one-layer 2D shapes at low μH and switch to compact 3D shapes under high μH, during which the Pt8 cluster preserves moderate fluxionality. Further analysis reveals a similar Pt–Pt bond length increase when switching from low μH to high μH on both surfaces although morphological transformations are different. Electronic structure analysis shows the existence of bonding interactions between Pt and Lewis acidic Al3+ sites along with the Pt–O interaction, which implies the necessity to include Al neighbors to discuss the electronic structure of small Pt clusters. [ABSTRACT FROM AUTHOR]